U.S. patent application number 12/460882 was filed with the patent office on 2011-01-27 for simple noise control method.
Invention is credited to Vuong Binh Hong.
Application Number | 20110018622 12/460882 |
Document ID | / |
Family ID | 43496767 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110018622 |
Kind Code |
A1 |
Hong; Vuong Binh |
January 27, 2011 |
Simple noise control method
Abstract
The Simple Noise Control Method is a method used to eliminate
all noise from a pulsed signal. By subjecting the pulsed signal to
a band pass filter and duration filter based on simple, low cost
and widely available timers, counters and logic gates or
equivalents, any noise in the pulsed signal which have different
frequencies or durations than the signal can be removed with very
high certainty.
Inventors: |
Hong; Vuong Binh; (Costa
Mesa, CA) |
Correspondence
Address: |
VUONG BINH HONG
3132 COOLIDGE AVE
COSTA MESA
CA
92626
US
|
Family ID: |
43496767 |
Appl. No.: |
12/460882 |
Filed: |
July 27, 2009 |
Current U.S.
Class: |
327/551 |
Current CPC
Class: |
H04B 15/04 20130101;
H03K 5/1252 20130101; H04B 2215/064 20130101 |
Class at
Publication: |
327/551 |
International
Class: |
H04B 1/10 20060101
H04B001/10 |
Claims
1) A Simple Noise Control Method: a method that virtually
eliminates all noise in a pulsed signal by using a band pass filter
and a duration filter to filter out the noises.
2) The Simple Noise Control Method of claim 1, wherein the band
pass filter and duration filter are comprised of timers, counters
and logic gates.
3) The Simple Noise Control Method of claim 2, wherein the band
pass filter is built by using three timers, two counters, one Or
gate, one And gate, and one inverter.
4) The Simple Noise Control Method of claim 3, wherein the three
timers generate three pulses of different length, one short, one
long and one which is the longest. The difference between the short
and long pulses depends on the consistent frequency of the signal
but it cannot be equal or longer than the short pulse for proper
operation. If the signal frequency is highly constant then the
difference is small and vice versa. The two counters are chosen
such that these two pulses enable the two counters when the pulses
are at high state and clear the two counters at low state. The
three timers are triggered by the same signal pulse to start the
three pulses almost at the same time.
5) The Simple Noise Control Method of claim 4, wherein the two
counters count the pulses of the signal within the short and long
periods of time generated by the two timers. Because the frequency
of the signal is known within certain limits, the length of the
pulse from the timer of the short pulse (short timer) can be
calculated as such that the short counter will count to certain
number and clock the flip flop only if the frequency of the signal
is equal or higher than the minimum frequency of the signal. This
will eliminate all noises which have frequencies that are lower
than the minimum frequency of the signal. The short counter works
as a high pass filter. On the other hand, the counter of the long
pulse (long counter) is supposed to NOT count to certain number at
the end of the pulse. If the long counter reaches a certain number
within the length of the long pulse, the frequency of the signal
(actually noise) is higher than the maximum frequency of the good
signal. If this happens, the long counter will toggle the flip flop
again thus canceling out the effect of the short counter. In short,
the long counter works as a low pass filter. During the longest
pulse, the output of the flip flop is rendered unable by the use of
an inverter and an and gate. At the end of the longest pulse, if
the flip flop changes its state, it means that the frequency of the
signal is within certain limit of the pass band. However, because
some noises can have frequencies within the frequency limits, the
output of the flip flop will need to be run under another filter,
the duration filter. The duration filter comprises the same
components as the band pass filter: three timers, two counters, one
flip flop, one And gate, one Or gate and one inverter gate. The
operation of the duration filter is similar to the operation of the
frequency pass band filter; however, the duration filter is based
on how long the signal is kept running not the frequency. As a
result, the noises existing for a period time which is shorter or
longer than the proper duration of the signal will be eliminated.
Usually, the noises are short but the long pulse test can be used
to eliminate the chance of a false trigger such as someone standing
in front of a touchless switch for a long period of time.
7) The Simple Noise Control Method of claim 1, wherein the output
of the flip flop of the duration filter can be used as a memory of
a switch and it can turn on or off an apparatus such as a lamp,
faucet etc. without worry about noise.
8) The Simple Noise Control Method of claim 1, wherein a high pass
filter and long duration filter can be used instead of a band pass
and a duration filters to filter out the noises. In that case, only
one timer and one counter are needed for each high pass filter or
long duration filter. Because noise is either fast and short or
slow and long, a high pass filter and a long duration filter can be
used effectively eliminate all noises from circuits or other uses.
The combination of many of these filters can create a machine free
of noise.
Description
[0001] The Simple Noise Control Method is a method used to control
the noise in a circuit which uses pulsed signals as a means of
communication. This method utilizes regular timers, counters and
logic IC's to prevent noises in signal from affecting the circuit.
The timers and counters create a frequency band pass filter and
duration filter which will virtually render the circuit noise
free.
[0002] The band pass filter eliminates all noises below and above a
minimum and maximum frequency limits in which the signal frequency
is well within or near the middle of the limits.
[0003] The duration filter eliminates all noises which frequencies
are within the pass band but their lives are shorter or longer than
certain time limits in which the signal is supposed to be
within.
[0004] The band pass filter can be modified very easily to become
high pass filters to use in a case the noises' frequencies are low.
The duration filter can also be modified as such easy to become a
long duration filter which filters out noises which have lives
shorter than the minimum time duration of the window. After these
two filters, the noises are virtually eliminated and the circuit is
noise free.
REFERENCE
TABLE-US-00001 [0005] 5,049,763 Sep. 17, 1991 Rogers 6,175,598 Jan.
16, 2001 Yu, et al.
[0006] U.S. Pat. No. 5,049,763, Rogers, Sep. 17, 1991, discloses a
ground noise detector circuit which can detect the ground noise
caused by the power supply and takes proper action to reduce the
damage caused by the noise. However, the Rogers, 1991 circuit has
the disadvantages of not detecting and protecting the device from
noises come from other sources such as surrounding or spike.
[0007] U.S. Pat. No. 6,175,598, Yu, et al., Jan. 16, 2001,
discloses an output noise control scheme for multiple I/O's which
can significantly reduce power ground bounce characteristics when
multiple outputs being simultaneously switched. However, the Yu, et
al, 2001 circuit has the disadvantages of not detecting and
protecting the circuit from noises come from other sources such as
spike which can falsely change the operation of the circuit.
BACKGROUND OF THE INVENTION
[0008] Interference from noise is a major problem for almost all
electronic circuits. Noise can come from a variety of sources,
including the surrounding environment, the power supply, the spike
on the electrical network especially from inductance device
connected to the same electrical conductors. Some devices can
tolerate certain levels of noises; however, some devices cannot
tolerate even a single noise which might effect its operation. A
touchless switch which mistakenly turns on the light while people
are sleeping is not acceptable.
[0009] There are many methods to control and to eliminate noises
such as noise suppressor diode to limit the Voltage of the spike, a
time delay circuit to wait out the noise or use of software
algorithms to eliminate noise. However, noises are unpredictable
and everywhere. It is costly to contain noises and sometimes it is
almost impossible to avoid them.
[0010] The present invention will control the noise in a circuit
which uses pulsed signals as an operation media. One typical
application, but not limited to, is a touchless switch using pulsed
infrared (IR) signals to control the switch. If a person reflects
an IR beam to the receiver, the switch will toggle. There are many
sources of noises: the sun, light and human, devices. Noise control
is critical for a touchless switch.
[0011] The present invention uses a few simple, low cost and widely
available integrated circuits such as timers, counters, logic gates
and flip flops to control the noises in the circuit. For the
example of a touchless switch, the IC's required to control the
noises are just two timers and two counters, with which they can
protect the switching circuit and keep it virtually free of
noise.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0012] The above and other aspects, features and advantages of the
present invention will be more apparent from the following more
particular description presented in conjunction with the following
drawings wherein:
[0013] FIG. 1 shows the block diagram of the typical frequency
filter circuit. The duration filter circuit is exactly the same
except the length of the wave form is much longer.
[0014] FIG. 2 shows the block diagram of a typical high pass filter
circuit and long duration pass filter circuit and the flip flop as
the memory cell for a simple circuit such as touchless switch
circuit.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The following description is of the best version presently
contemplated for carrying out the invention. This description is
not to be taken in a limiting sense, but is made merely for the
purpose of describing one or more preferred embodiments of the
invention. The scope of the invention should be determined with
reference to the claims.
[0016] The present invention provides a simple but effective method
to control the noises introduced into the signal at the input of
the circuit by the surrounding environment or power supply.
[0017] From FIG. 1 three timers 1, 2 and 3 generate three pulses:
one short, one long and one longest. The difference between the
short and long pulses depends on the consistent frequency of the
signal but it cannot be equal or longer than the short pulse for
proper operation. If the signal frequency is highly constant then
the difference is small and vice versa. These two pulses enable
counters 4 and 5 at high state and clear the two counters 4 and 5
at low state. Three timers 1, 2 and 3 are triggered by the same
signal pulse to start the three pulses almost at the same time.
[0018] Counters 4 and 5 count the pulses of the signal within the
short and long periods of time generated by timers 1 and 2,
respectfully. Because the frequency of the signal is known within
certain limits, the length of the pulse from timer can be
calculated such that counter 4 will count to certain number and
clock the flip flop 8 only if the frequency of the signal is equal
or higher than the minimum frequency of the signal. Thus this will
eliminate all noise which has frequencies lower than the minimum
frequency of the signal. Counter 4 works as a high pass filter. On
the other hand, counter 5 is supposed NOT to count to certain
number at the end of the pulse. If counter 5 reaches certain number
within the length of the long pulse, the frequency of the signal
(actually noise) is higher than the maximum frequency of a good
signal. If this happens, counter 5 will toggle flip flop 8 again
thus canceling out the effect of counter 4. As a result, counter 5
works as a low pass filter. Or gate 7 is used to connect two
outputs of counter 4 and 5 to the clock input of flip flop 8.
During the longest pulse, the output of flip flop 8 is rendered
unable by the use of inverter 6 combined with and gate 9. At the
end of the longest pulse, and if the flip flop 8 changes its
states, the frequency of the signal will be within certain limit of
the band pass and the signal is good.
[0019] However, because some noises can have frequencies comparable
to the good signal, the output of flip flop 8 is needed to run
under another filter: the duration filter.
[0020] The duration filter which is the same as the band pass
filter is comprised of three timers, two counters, one flip flop,
one and, one or and one inverter gates. The operation of the
duration filter is exactly the same as the operation of the band
pass filter; however, the duration filter is based on how long the
signal is kept under test, not the frequency. Noise which duration
is shorter or longer than the supposed duration of the signal will
be eliminated. Usually, noise's duration is short but the long
pulse test can be used to eliminate the chance of a false trigger,
such as someone standing in front of a touchless switch for a long
period of time.
[0021] The output of the flip flop of the duration filter can be
used to turn on or off an apparatus such as a lamp, faucet etc,
without worrying about noises in the input signal.
[0022] FIG. 2 shows the block diagram of a reduced Simple Noise
Control Method circuit. A high pass filter and long duration filter
can be used instead of the band pass filter and the duration filter
to filter out the noises. In this case, only one timer 10 and one
counter 11 are needed for the high pass filter and timer 12,
counter 13 are needed for the long duration filter. Flip flop 14 is
used to remember the state of the circuit. Because the nature of
noise is either fast and short or slow and long, a high pass filter
and a long duration filter can be used effectively to eliminate all
noises for a switch circuit or other devices. The combination of
many of these filters can create a machine in which noises are
effectively avoided.
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